Set PerThreadCache as readonly when formatting change e-mails

Apply the same optimisation made for Change-Id: I1b71bfcf to
the formatting the change e-mails body, which is done
synchronously to the incoming REST API and thus impacts
the latency perceived by the end user.

The composition of the e-mail is using multiple information
coming from multiple fields from NoteDb and calls the /meta
refs lookups multiple times for the same change.

The same considerations of performance improvement and reduction
of /meta refs lookup are valid in this use-case.

Release-Notes: enable the read-only cache of /meta when producing JSON
Change-Id: I993d4ddc37cf27b66ea9d7323963e761564603fa

3 files changed, 128 insertions, 118 deletions

diff --git a/java/com/google/gerrit/server/mail/send/ChangeEmail.java b/java/com/google/gerrit/server/mail/send/ChangeEmail.java
index 924ab2def9..e0378741e9 100644
--- a/java/com/google/gerrit/server/mail/send/ChangeEmail.java
+++ b/java/com/google/gerrit/server/mail/send/ChangeEmail.java
@@ -85,7 +85,7 @@ public abstract class ChangeEmail extends NotificationEmail {
   protected boolean emailOnlyAuthors;
 
   protected ChangeEmail(EmailArguments ea, String mc, ChangeData cd) throws OrmException {
-    super(ea, mc, cd.change().getDest());
+    super(ea, mc, cd);
     changeData = cd;
     change = cd.change();
     emailOnlyAuthors = false;
diff --git a/java/com/google/gerrit/server/mail/send/NotificationEmail.java b/java/com/google/gerrit/server/mail/send/NotificationEmail.java
index be593ff9f2..09c6bf7acb 100644
--- a/java/com/google/gerrit/server/mail/send/NotificationEmail.java
+++ b/java/com/google/gerrit/server/mail/send/NotificationEmail.java
@@ -24,7 +24,10 @@ import com.google.gerrit.mail.MailHeader;
 import com.google.gerrit.reviewdb.client.Account;
 import com.google.gerrit.reviewdb.client.Branch;
 import com.google.gerrit.server.account.ProjectWatches.NotifyType;
+import com.google.gerrit.server.cache.PerThreadCache;
+import com.google.gerrit.server.cache.PerThreadCache.ReadonlyRequestWindow;
 import com.google.gerrit.server.mail.send.ProjectWatch.Watchers;
+import com.google.gerrit.server.query.change.ChangeData;
 import com.google.gwtorm.server.OrmException;
 import java.util.HashMap;
 import java.util.Map;
@@ -35,9 +38,11 @@ public abstract class NotificationEmail extends OutgoingEmail {
 
   protected Branch.NameKey branch;
 
-  protected NotificationEmail(EmailArguments ea, String mc, Branch.NameKey branch) {
+  protected NotificationEmail(EmailArguments ea, String mc, ChangeData cd) throws OrmException {
     super(ea, mc);
-    this.branch = branch;
+    try (ReadonlyRequestWindow window = PerThreadCache.openReadonlyRequestWindow()) {
+      this.branch = cd.change().getDest();
+    }
   }
 
   @Override
diff --git a/java/com/google/gerrit/server/mail/send/OutgoingEmail.java b/java/com/google/gerrit/server/mail/send/OutgoingEmail.java
index cd6882fc0e..608057309b 100644
--- a/java/com/google/gerrit/server/mail/send/OutgoingEmail.java
+++ b/java/com/google/gerrit/server/mail/send/OutgoingEmail.java
@@ -35,6 +35,8 @@ import com.google.gerrit.mail.MailHeader;
 import com.google.gerrit.reviewdb.client.Account;
 import com.google.gerrit.reviewdb.client.UserIdentity;
 import com.google.gerrit.server.account.AccountState;
+import com.google.gerrit.server.cache.PerThreadCache;
+import com.google.gerrit.server.cache.PerThreadCache.ReadonlyRequestWindow;
 import com.google.gerrit.server.permissions.PermissionBackendException;
 import com.google.gerrit.server.validators.OutgoingEmailValidationListener;
 import com.google.gerrit.server.validators.ValidationException;
@@ -99,138 +101,141 @@ public abstract class OutgoingEmail {
    * @throws EmailException
    */
   public void send() throws EmailException {
-    if (!args.emailSender.isEnabled()) {
-      // Server has explicitly disabled email sending.
-      //
-      logger.atFine().log(
-          "Not sending '%s': Email sending is disabled by server config", messageClass);
-      return;
-    }
+    try (ReadonlyRequestWindow window = PerThreadCache.openReadonlyRequestWindow()) {
+      if (!args.emailSender.isEnabled()) {
+        // Server has explicitly disabled email sending.
+        //
+        logger.atFine().log(
+            "Not sending '%s': Email sending is disabled by server config", messageClass);
+        return;
+      }
 
-    if (NotifyHandling.NONE.equals(notify) && accountsToNotify.isEmpty()) {
-      logger.atFine().log("Not sending '%s': Notify handling is NONE", messageClass);
-      return;
-    }
+      if (NotifyHandling.NONE.equals(notify) && accountsToNotify.isEmpty()) {
+        logger.atFine().log("Not sending '%s': Notify handling is NONE", messageClass);
+        return;
+      }
 
-    init();
-    if (useHtml()) {
-      appendHtml(soyHtmlTemplate("HeaderHtml"));
-    }
-    format();
-    appendText(textTemplate("Footer"));
-    if (useHtml()) {
-      appendHtml(soyHtmlTemplate("FooterHtml"));
-    }
+      init();
+      if (useHtml()) {
+        appendHtml(soyHtmlTemplate("HeaderHtml"));
+      }
+      format();
+      appendText(textTemplate("Footer"));
+      if (useHtml()) {
+        appendHtml(soyHtmlTemplate("FooterHtml"));
+      }
 
-    Set<Address> smtpRcptToPlaintextOnly = new HashSet<>();
-    if (shouldSendMessage()) {
-      if (fromId != null) {
-        Optional<AccountState> fromUser = args.accountCache.get(fromId);
-        if (fromUser.isPresent()) {
-          GeneralPreferencesInfo senderPrefs = fromUser.get().getGeneralPreferences();
-          if (senderPrefs != null && senderPrefs.getEmailStrategy() == CC_ON_OWN_COMMENTS) {
-            // If we are impersonating a user, make sure they receive a CC of
-            // this message so they can always review and audit what we sent
-            // on their behalf to others.
-            //
-            add(RecipientType.CC, fromId);
-          } else if (!accountsToNotify.containsValue(fromId) && rcptTo.remove(fromId)) {
-            // If they don't want a copy, but we queued one up anyway,
-            // drop them from the recipient lists.
-            //
-            removeUser(fromUser.get().getAccount());
+      Set<Address> smtpRcptToPlaintextOnly = new HashSet<>();
+      if (shouldSendMessage()) {
+        if (fromId != null) {
+          Optional<AccountState> fromUser = args.accountCache.get(fromId);
+          if (fromUser.isPresent()) {
+            GeneralPreferencesInfo senderPrefs = fromUser.get().getGeneralPreferences();
+            if (senderPrefs != null && senderPrefs.getEmailStrategy() == CC_ON_OWN_COMMENTS) {
+              // If we are impersonating a user, make sure they receive a CC of
+              // this message so they can always review and audit what we sent
+              // on their behalf to others.
+              //
+              add(RecipientType.CC, fromId);
+            } else if (!accountsToNotify.containsValue(fromId) && rcptTo.remove(fromId)) {
+              // If they don't want a copy, but we queued one up anyway,
+              // drop them from the recipient lists.
+              //
+              removeUser(fromUser.get().getAccount());
+            }
           }
         }
-      }
-      // Check the preferences of all recipients. If any user has disabled
-      // his email notifications then drop him from recipients' list.
-      // In addition, check if users only want to receive plaintext email.
-      for (Account.Id id : rcptTo) {
-        Optional<AccountState> thisUser = args.accountCache.get(id);
-        if (thisUser.isPresent()) {
-          Account thisUserAccount = thisUser.get().getAccount();
-          GeneralPreferencesInfo prefs = thisUser.get().getGeneralPreferences();
-          if (prefs == null || prefs.getEmailStrategy() == DISABLED) {
-            removeUser(thisUserAccount);
-          } else if (useHtml() && prefs.getEmailFormat() == EmailFormat.PLAINTEXT) {
-            removeUser(thisUserAccount);
-            smtpRcptToPlaintextOnly.add(
-                new Address(thisUserAccount.getFullName(), thisUserAccount.getPreferredEmail()));
+        // Check the preferences of all recipients. If any user has disabled
+        // his email notifications then drop him from recipients' list.
+        // In addition, check if users only want to receive plaintext email.
+        for (Account.Id id : rcptTo) {
+          Optional<AccountState> thisUser = args.accountCache.get(id);
+          if (thisUser.isPresent()) {
+            Account thisUserAccount = thisUser.get().getAccount();
+            GeneralPreferencesInfo prefs = thisUser.get().getGeneralPreferences();
+            if (prefs == null || prefs.getEmailStrategy() == DISABLED) {
+              removeUser(thisUserAccount);
+            } else if (useHtml() && prefs.getEmailFormat() == EmailFormat.PLAINTEXT) {
+              removeUser(thisUserAccount);
+              smtpRcptToPlaintextOnly.add(
+                  new Address(thisUserAccount.getFullName(), thisUserAccount.getPreferredEmail()));
+            }
+          }
+          if (smtpRcptTo.isEmpty() && smtpRcptToPlaintextOnly.isEmpty()) {
+            logger.atFine().log("Not sending '%s': No SMTP recipients", messageClass);
+            return;
           }
         }
-        if (smtpRcptTo.isEmpty() && smtpRcptToPlaintextOnly.isEmpty()) {
-          logger.atFine().log("Not sending '%s': No SMTP recipients", messageClass);
-          return;
-        }
-      }
 
-      // Set Reply-To only if it hasn't been set by a child class
-      // Reply-To will already be populated for the message types where Gerrit supports
-      // inbound email replies.
-      if (!headers.containsKey(FieldName.REPLY_TO)) {
-        StringJoiner j = new StringJoiner(", ");
-        if (fromId != null) {
-          Address address = toAddress(fromId);
-          if (address != null) {
-            j.add(address.getEmail());
+        // Set Reply-To only if it hasn't been set by a child class
+        // Reply-To will already be populated for the message types where Gerrit supports
+        // inbound email replies.
+        if (!headers.containsKey(FieldName.REPLY_TO)) {
+          StringJoiner j = new StringJoiner(", ");
+          if (fromId != null) {
+            Address address = toAddress(fromId);
+            if (address != null) {
+              j.add(address.getEmail());
+            }
           }
+          smtpRcptTo.stream().forEach(a -> j.add(a.getEmail()));
+          smtpRcptToPlaintextOnly.stream().forEach(a -> j.add(a.getEmail()));
+          setHeader(FieldName.REPLY_TO, j.toString());
         }
-        smtpRcptTo.stream().forEach(a -> j.add(a.getEmail()));
-        smtpRcptToPlaintextOnly.stream().forEach(a -> j.add(a.getEmail()));
-        setHeader(FieldName.REPLY_TO, j.toString());
-      }
-
-      String textPart = textBody.toString();
-      OutgoingEmailValidationListener.Args va = new OutgoingEmailValidationListener.Args();
-      va.messageClass = messageClass;
-      va.smtpFromAddress = smtpFromAddress;
-      va.smtpRcptTo = smtpRcptTo;
-      va.headers = headers;
-      va.body = textPart;
 
-      if (useHtml()) {
-        va.htmlBody = htmlBody.toString();
-      } else {
-        va.htmlBody = null;
-      }
+        String textPart = textBody.toString();
+        OutgoingEmailValidationListener.Args va = new OutgoingEmailValidationListener.Args();
+        va.messageClass = messageClass;
+        va.smtpFromAddress = smtpFromAddress;
+        va.smtpRcptTo = smtpRcptTo;
+        va.headers = headers;
+        va.body = textPart;
+
+        if (useHtml()) {
+          va.htmlBody = htmlBody.toString();
+        } else {
+          va.htmlBody = null;
+        }
 
-      for (OutgoingEmailValidationListener validator : args.outgoingEmailValidationListeners) {
-        try {
-          validator.validateOutgoingEmail(va);
-        } catch (ValidationException e) {
-          logger.atFine().log(
-              "Not sending '%s': Rejected by outgoing email validator: %s",
-              messageClass, e.getMessage());
-          return;
+        for (OutgoingEmailValidationListener validator : args.outgoingEmailValidationListeners) {
+          try {
+            validator.validateOutgoingEmail(va);
+          } catch (ValidationException e) {
+            logger.atFine().log(
+                "Not sending '%s': Rejected by outgoing email validator: %s",
+                messageClass, e.getMessage());
+            return;
+          }
         }
-      }
 
-      Set<Address> intersection = Sets.intersection(va.smtpRcptTo, smtpRcptToPlaintextOnly);
-      if (!intersection.isEmpty()) {
-        logger.atSevere().log("Email '%s' will be sent twice to %s", messageClass, intersection);
-      }
+        Set<Address> intersection = Sets.intersection(va.smtpRcptTo, smtpRcptToPlaintextOnly);
+        if (!intersection.isEmpty()) {
+          logger.atSevere().log("Email '%s' will be sent twice to %s", messageClass, intersection);
+        }
 
-      if (!va.smtpRcptTo.isEmpty()) {
-        // Send multipart message
-        logger.atFine().log("Sending multipart '%s'", messageClass);
-        args.emailSender.send(va.smtpFromAddress, va.smtpRcptTo, va.headers, va.body, va.htmlBody);
-      }
+        if (!va.smtpRcptTo.isEmpty()) {
+          // Send multipart message
+          logger.atFine().log("Sending multipart '%s'", messageClass);
+          args.emailSender.send(
+              va.smtpFromAddress, va.smtpRcptTo, va.headers, va.body, va.htmlBody);
+        }
 
-      if (!smtpRcptToPlaintextOnly.isEmpty()) {
-        logger.atFine().log("Sending plaintext '%s'", messageClass);
-        // Send plaintext message
-        Map<String, EmailHeader> shallowCopy = new HashMap<>();
-        shallowCopy.putAll(headers);
-        // Remove To and Cc
-        shallowCopy.remove(FieldName.TO);
-        shallowCopy.remove(FieldName.CC);
-        for (Address a : smtpRcptToPlaintextOnly) {
-          // Add new To
-          EmailHeader.AddressList to = new EmailHeader.AddressList();
-          to.add(a);
-          shallowCopy.put(FieldName.TO, to);
+        if (!smtpRcptToPlaintextOnly.isEmpty()) {
+          logger.atFine().log("Sending plaintext '%s'", messageClass);
+          // Send plaintext message
+          Map<String, EmailHeader> shallowCopy = new HashMap<>();
+          shallowCopy.putAll(headers);
+          // Remove To and Cc
+          shallowCopy.remove(FieldName.TO);
+          shallowCopy.remove(FieldName.CC);
+          for (Address a : smtpRcptToPlaintextOnly) {
+            // Add new To
+            EmailHeader.AddressList to = new EmailHeader.AddressList();
+            to.add(a);
+            shallowCopy.put(FieldName.TO, to);
+          }
+          args.emailSender.send(va.smtpFromAddress, smtpRcptToPlaintextOnly, shallowCopy, va.body);
         }
-        args.emailSender.send(va.smtpFromAddress, smtpRcptToPlaintextOnly, shallowCopy, va.body);
       }
     }
   }